Unraveling the structural basis for freeze-thaw stability of emulsion-filled soybean protein isolate-arabinoxylan double network gels

An emulsion with a consistent average droplet size, stabilized by either Tween20 or soy protein isolate (SPI), was added into a SPI/arabinoxylan (AX) double-network gel matrix to create emulsion-filled gels (EFGs). The emulsifier type and SPI/AX matrix composition affected the freeze-thaw stability of EFGs via changing interactions of interfacial and matrix interactions. The results of Fourier transform infrared spectroscopy, Fluorescence spectroscopy, Molecular docking and Dynamics simulations confirmed that more hydrogen bonds formed between the SPI molecules than between Tween20 and SPI. Thermogravimetric analysis also revealed that interfacial SPI was bonded with gel matrix and integrated into the network. During freeze-thaw cycles, stronger molecular interactions and a more interconnected network delayed β-sheet formation and protein reorganization. SPI/AX ratio affected the freeze-thaw stability via changing molecular interaction among macromolecule of gel matrix. A higher proportion of AX exhibited the strengthened interactions with SPI matrix. This delayed the protein denaturation and phase separation of the double networks. EFG with higher AX content tended to adopt a more ordered conformation, as evidenced by an increase in the α-helix content during freeze-thaw cycles. These findings indicate that matrix and interfacial interactions enhance freeze-thaw stability, significantly expanding the application of emulsion-filled double-network gels in frozen foods.